Condensate removal system for rotary drums



Oct. 4, 1966 H. W. BARNSCHEIDT ET AL CONDENSATE REMOVAL SYSTEM FOR ROTARY DRUMS Filed March 15, 1962 Fig.7

HANS WOLFGANG EARNSCl/E/DT WEE/V51? MA/WVH/MDT United States Patent 3,276,141 CONDENSATE REMOVAL SYSTEM FOR ROTARY DRUMS Hans Wolfgang Barnscheidt, Dusseldorf, and Werner Mannhardt, Stuttgart-Vaihingen, Germany, assignors to J. M. Voith Gesellschaft mit beschrankter Haftung, Heidenheim (Brenz), Germany Filed Mar. 15, 1962, Ser. No. 179,901

5 Claims. (Cl. 34-125) The present invention relates to the removal of condensate from the inner surface of a steam-heated rotary drum, more particularly, to a device within a rotary drum for more effectively removing the condensate therefrom without physical contact with the inner periphery of the rotating drum.

In steam-heated drums which rotate at high peripheral speeds, for example drying cylinders for paper machines, the condensate from the steam within the drum forms a film of water of a substantially uniform thickness on the inner surface of the drum under the action of frictional and centrifugal forces caused by the rotation of the drum. This liquid film is disadvantageous because it adversely affects heat conduction through the wall of the drum, such heat conduction decreasing as the thickness of this liquid film increases. Decreased conduction of heat through the wall of the drum results in lower temperatures on the outer surface of the drum so that the outer surface temperature of the drum will decrease as the thickness of the film increases, even though the temperature of the steam within the drum remains constant. In addition, when the thickness of the liquid film becomes excessive, the possibility arises of having areas on the outer surface of the drum which are at different temperatures. These varying temperature areas are particularly disadvantageous on drying cylinders in paper making machinery since they adversely affect the quality of the paper.

Accordingly, considerable effort has been spent in attempts to eliminate the liquid film from the inner surface of the drum. For physical reasons it is not possible to entirely eliminate this liquid film. Accordingly, the thickness of the film can be reduced only to a certain minimum value.

One of the devised structures for eliminating the condensate film from the inner surface of a rotating drum comprises a stationary nozzle having an open face which is directed towards the inner surface of the drum. The nozzle is connected to a radially extending pipe which is then bent into an axially extending pipe which passes outwardly of the drum through one of the supporting trunnions. The leading edge of the nozzle is positioned at a greater distance than the other edges of the nozzle. Accordingly, an opening is formed in the nozzle which is able to act in opposition to the film of liquid on the rotating drum. This liquid is caught under the leading edge of the nozzle whenever the thickness of the film exceeds the distance between the other nozzle edges and the inner surface of the drum. The impact pressure caused by the liquid impinging into the nozzle opening under the leading edge thereof forces the liquid through the radial and axial pipes to a reservoir located exteriorly of the drum.

This nozzle has the disadvantage of being able to reduce the thickness of the liquid film only to the distance between the trailing edge of the nozzle and the inner surface of the drum. However, the trailing edge of the nozzle cannot be positioned any closer than two millimeters from the inner surface of the drum. If positioned less than two millimeters, there is the possibility of the nozzle contacting the inner surface of the drum 3,275,141 Patented Oct. 4, 1966 during the rotating there-of and thus eventually causing damage to both the nozzle and the drum. Such a contact between the nozzle and the drum might be caused by differences in the coefficient of therrnoexpansion of the drum and the nozzle piping or irregularities in the inner surface of the drum. It is therefore apparent that the thickness of the liquid condensate film cannot be reduced to less than two millimeters using the prior art arrangements.

Another form of a stationary arrangement for removing condensate from a drum comprises a hollow enclosed body having a triangular base which is closed and is directed towards the inner surface of the drum. The body, however, is open along the base of the triangle which base forms the leading edge of the nozzle. This base line is parallel to the axis of the rotating drum. However, here again, the thickness of the liquid film cannot be reduced to less than the distance between the opening of the nozzle and the inner surface of the drum.

One proposed solution has been to construct the nozzle of a material which will permit the nozzle to contact the inner surface of the drum without damaging either the drum or the nozzle. This could mean a reduction in the distance between the open edge of the nozzle and the inner surface of the drum. This nozzle was also mounted in such a manner that the nozzle opening would follow irregularities in the drum. However, it still was not possible to reduce the thickness of the liquid film formed beyond the above-mentioned thickness of two millimeters.

It is noted that in one modification the nozzle was rotated with respect to the inner surface of the drum, however, this modification required a substantial increase in the power necessary for driving the drum, and accord- .ingly, was not accepted.

It is therefore the principal object of this invention to provide a novel and improved arrangement for removing condensate from a steam-heated rotary drum.

It is another object of this invention to provide a novel and improved arrangement for reducing the film of water on the inner surface of a rotary drum.

It is a further object of this invention to provide a novel and improved arrangement for reducing the thickness of a film of water on the inner surface of a rotating drum without physical contact between the arrangement and the drum inner surface.

The present invention proposes to eliminate the abovementioned disadvantages of prior art structures and to achieve the objects of this invention by positioning the open face of a nozzle in such a manner that this open face is approximately parallel to the inner surface of the drum. The nozzle is so positioned that the surfaces defined by the edges of the nozzle opening have all portions thereof approximately equidistant from the inner surface of the drum. It has been found that this arrangement will permit the removal of a greater quantity of liquid than has been possible in previous known condensate removal systems. In addition, the nozzle arrangement of this invention achieves this result without reducing the space between the edges of the nozzle opening and the inner surface of the drum to less than the space used in previous arrangements. The thickness of the liquid film can be reduced to a thickness less than the distance between the nozzle opening and the inner surf-ace of the drum by establishing a difference in pressures between the inner surface of the drum and the reservoir into which the condensate is passed.

It appears that the nozzle of this invention removes a greater quantity of liquid from the film on the inner surface. The amount of the steam in the drum which enters the nozzle at a high speed through the opening formed between the surface of the liquid and the leading edge of the nozzle opening serves to pick up and carry with it quantities of liquid from the uppermost layers of the liquid film. By measuring the quantity of water remaining in the drum after the operation of the nozzle of this invention, it was conclusively proved that the thickness of the film which can be obtained by the nozzle of this invention is substantially smaller than the thickness of the film obtained with previously known devices. In addition, measurements of the temperature on the outer surface of the drum show that higher temperatures were obtained even though the temperature of the steam within the drum remained the same as that when using prior art condensate removing systems. These temperature measurements also confirm the existence of a thinner film of liquid when using the nozzles of the present invention.

One embodiment of the present invention comprises a nozzle which is essentially a tubular member with one end being open and the other end being closed. The open end is directed towards the inner surface of the drum and the closed end has a centrally located aperture to which is connected a pipe which leads outwardly of the drum through the trunnion. The side walls of the nozzle are formed from the wall of the tubular member substantially perpendicular to the closed end face of the nozzle. The cross-section of the tubular member may 'be quadrangular, rectangular or trapezoidal. This construction provides a nozzle edge of sufiicient length to permit the passage of liquid through the slot formed between the edge of the nozzle opening and the inner surface of the drum. With this shaped nozzle uneconomical costs of manufacturing the nozzle are avoided.

Other objects and advantages of this invention will be apparent upon reference to the accompanying description when taken in conjunction with the following drawings, wherein [FIGURE 1 is a sectional view, taken along the longitudinal axis of a steam-heated drying cylinder of a paper machine, and showing the condensate removal device within the drum;

FIGURE 2 is a perspective view of the nozzle of this invention such as that employed in FIGURE 1;

FIGURE 3 is a bottom plan view of a modification of the nozzle of this invention;

FIGURE 4 is a front elevational view of the nozzle illustrated in FIGURE 3;

FIGURE 5 is a sectional view, taken along the line AA of FIGURE 3, and showing the relationship of the nozzle with respect to the inner surface of the drum.

A specific embodiment and modifications of this invention will be described in detail with reference to the accompanying drawings wherein like reference symbols indicate the same parts throughout the various views.

Returning to FIGURE 1 there is shown a steam-heated drying cylinder 1 of a paper machine, which cylinder comprises a cylindrical wall 2. The cylinder is mounted upon trunnions, one of the trunnions 3 being hollow. Within the cylinder is a radially extending pipe 4 which connects with a pipe 4a which is coaxial with the cylinder '1. The pipe 4a passes through the hollow trunnion '3 to connect with a reservoir for holding the liquid removed from the interior of the drum. The condensate removal device is completed by a nozzle 5 which is mounted on the outer end of the pipe 4.

The nozzle 5 is illustrated in detail in FIGURE 2 where it can be seen that the nozzle comprises a hollow boxlike member having a rectangular cross-section with a closed end plate 6 and an open end 6a. The open end 6a is directed towards the inner surface of the cylindrical wall 2. The closed end plate 6 has a central aperture 8 which is connected to the radially extending pipe 4. The nozzle has two short side walls 7 which are perpendicular, and two longer side walls 7b and 70 which are parallel to the rotary axis of the cylinder 1 When the nozzle is in the position as illustrated in FIG- 4. URE 1. The edges of the walls 7, 7b and 7c are indicated at 7a.

It has been found that it is not necessary to construct the edges 7a of the nozzle opening so as to define a cylindrical surface which is concentric to the shell of the drying cylinder with all points on the edges 7a of the nozzle equidistant from the inner surface of the drum wall 2. This is particularly true When the lengths of the side walls 7 are small in comparison with the diameter of the drying drum. It is therefore possible to construct the nozzle so that the edges of the opening define a plane substantially parallel to the inner surface of the drum when the nozzle is in position. The relatively large radius of curvature of the drum will insure that all points in this plane are approximately equidistant from the inner surface of the drum wall 2. Since the inner surface is curved, it can be more accurately stated that the plane formed by the nozzle opening edges 7a is perpendicular to a radius of the drum which radius passes through the center of the nozzle 5. Since the aperture 8 has its center at the point of intersection of the diagonals of the rectangular plate 6, it is apparent that this radius will pass through this point of intersection. The construction of the nozzle with the edges of the opening forming a plane will greatly simplify its fabrication.

Proceeding next to FIGURES 3, 4 and 5 there is illustrated a modification of this invention wherein the nozzle 5 is similar to the nozzle as illustrated in FIG- URE 2 but comprises a trapezoidal cross-section with the parallel edges 7b and 7c of the nozzle 5 being arranged parallel to the rotary axis of the drum when the nozzle is in position. The side walls 7 are the non-parallel edges of the trapezoid. This modification is particularly advantageous since a large portion of the nozzle edge is positioned perpendicularly to the direction of rotation of the condensate film and this position creates favorable conditions for the aspiration of the liquid from the film by the nozzle. With this modification it is desirable that each of the two parallel edges of the trapezoid is longer than one of the non-parallel sides of the trapezoid. The longer of the parallel sides is positioned so as to form the leading edge of the nozzle.

In FIGURE 5 the wall of the drum which rotates in the direction as indicated by the arrow B is drawn in dashed lines so as to indicate the relative position between the operating nozzle 5 and the inner surface of the drum wall 2. A film of liquid on the inner surface of the drum wall 2 is indicated at C. A narrow slot is formed at D between the leading edge at 711 of the nozzle opening and the inner surface of the drum wall 2. The steam in the drum rushes through this slot D in a direction as indicated by the arrow and carries along a portion of the liquid film, as also indicated in FIGURE 5. Accordingly, the liquid film will contact the edges of the nozzle opening even though the nozzle opening is positioned above the top surface of the film, as can be seen in FIG- URE 5. By this action of the steam under the leading edge of the nozzle it is possible to remove water from this liquid film even though the thickness of this film is less than the distance between the edge of the nozzle and the inner surface of the drum.

Reference to FIGURE 1 will show that the connecting branch 6b extending from the nozzle for connection to the pipe 4 has a constricted portion 9 with a reduced crosssection relative to the cross-section of the pipe 4.

The constricted portion functions to adapt the quantity of liquid which is to be removed from the drum to the different accumulations of condensate which may be found in different drying cylinders. The degree of constriction and the area of this reduced cross-section are dependent upon the operational conditions in each case.

The condensate removing equipment of the present invention, in addition to the constricted portion 9, may comprise an aperture 10 in the wall of the radial pipe 4. This aperture 14) is positioned in the wall of the pipe 4 behind the constricted portion 9 and above this portion, as viewed in FIGURE 1. With this construction steam will flow through the aperture at a high speed in those cases where the slot between the nozzle edge 7a and the inner surface of the drum wall 2 is obstructed by a thick film of condensate. Then, the steam flowing in through the aperture 10 is not choked or throttled by the reduced cross-section of the constricted portion 9. Consequently, this steam at a given difference in pressure will achieve its highest possible rate of flow without being affected by the reduced cross-section of the constricted portion 9.

'Thus, the use of the aperture 10 will permit a quick removal of condensate from the drum down to a normal thickness of the condensate film in those cases where a much greater quantity of liquid than usual temporarily occurs in the drum. Consequently, the distance of the aperture 10 from the inner surface of the drum wall 2 should be greater than the maximum possible thickness of the condensate film that could be expected under abnormal operation conditions. Such abnormal conditions might arise when a paper machine having the drum mounted in the dry section thereof starts to operate from a cold condition. Another abnormal case is when there exist transitory differences in pressure between the normal pressure prevailing in the interior of the drum and that prevailing in the condensate storage tank. Under these conditions steam may readily enter in the radial pipe 4 through the aperture 10 when the thickness or the depth of the liquid is such that steam cannot enter through the nozzle under the front edge thereof. Steam flowing through the aperture will create a pressure differential within the nozzle which differential is dependent upon the speed at which the steam flows into the aperture. As a result of this pressure differential a vacuum is formed which permits a large quantity of liquid to be rapidly drawn off by the nozzle. Thus the aperture also enables the condensate removal process to quickly begin as soon as the drum starts to rotate.

The effectiveness of the nozzle of this invention can best be illustrated by reference to a specific operating example. A rotary drying cylinder having a diameter of 1.5 meters and a length of 5 meters was rotated in a paper machine at a peripheral speed of 600 meters per minute. The edge of the nozzle opening was positioned 2 millimeters from the inner surface of the drying cylinder wall. There was a difference of 0.25 atmosphere of pressure between the pressure in the interior of the drying cylinder and the condensate storage tank. A virtually constant surface temperature of 109 C. was obtained on the outer surface of the drying cylinder wall. When a condensate removal nozzle of the type described above as comprising the prior art was used, the surface temperature of the drying cylinder was only 101 C. under the same conditions with the distance between the nozzle opening edge and the inner surface of the cylinder wall also being 2 millimeters.

The nozzle of this invention was progressively moved away from the inner surface of the cylinder wall so as to increase the distance between the nozzle opening edge and the inner surface of the wall from 2 millimeters up to 5 millimeters. In all cases, however, the temperature of the outer surface of the drying cylinder wall remained 109 C. When the prior art nozzle was progressively moved away from the cylinder wall, the outer surface temperature dropped from 101 C. at a distance of 2 millimeters to 93 C. at a distance of 3 millimeters. This outer surface temperature dropped substantially more when this space was further increased.

These experiments demonstrated the vastly improved results which can be obtained with the nozzle of this invention not only when the space between the nozzle opening and the inner surface of the drum remains constant during rotation of the drum, but also when this space varies. For this reason the nozzle of this invention can readily be used when the inner surface of the drum has irregularities or when the drum has an inaccurate rotation.

The nozzle of this invention can also be used for other purposes rather than in steam-heated rotary drying cylinders of paper making machines as described above. This nozzle can be used in all high-speed rotary drums or the like where it is desirable to maintain the thickness of a liquid film over the inner surface of the drum at a predetermined minimum. One such use is with cooling cylinders arranged in the end of the dry section of a paper making machine. In this instance it is essential to eliminate the warm water accumulating on the inner surface of the cylindrical shell so that fresh cooling water can contact this inner surface. No high pressure steam is here available for assistance in removing the warm cooling water. Accordingly, any gas which may be similar to steam is introduced into the interior of the cylinder either mixed with the incoming cooling water or separated therefrom. The presence of the gas enables the nozzle to operate in the manner as described above. This operation does not require any additional installations since it is only necessary that the differences in pressure between the interior of the cylinder and the condensate storage tank are equal to at least the flow resistance of the liquid when flowing from the nozzle to the storage tank. Further, that portion of the interior of the cylinder which is not filled by the cooling water is occupied by a gas which, in most cases, is atmospheric air to which this pressure differential may be imparted.

Thus it can be seen that the present invention provides an improved installation for removing condensate from the interior of a steam-heated rotary drying drum. Further, the operation of the condensate removal nozzle of this invention is independent of the distance between the nozzle and the inner surface of the drum. Accordingly, a much greater quantity of condensate can be removed from the interior of the drum than has been previously possible.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions and, accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

What is claimed as this invention is:

1. A condensate removal system for a horizontal drum with a hollow trunnion, said system comprising a horizontal pipe coaxial with the trunnion, a stationary radial pipe supported by and extending substantially at right angles from the horizontal pipe and an intake nozzle on the lower end of said radial pipe, said intake nozzle comprising a hollow boxlike structure completely closed on all sides by vertical walls around its horizontal periphery but with an open bottom and with an apertured top connected with the radial pipe and providing a passageway in communication therewith, the entire lower edge of the nozzle lying in an approximately horizontal plane close to but spaced slightly above the inner surface of the drum and adapted to remain in said plane during the rotation of the drum.

2. The system of claim 1, in which the lower edge of the nozzle is trapezoidal in form, the two parallel edges of the trapezoid being parallel to the axis of the drum.

3. The system of claim 1, in which the walls of the passageway to the radial pipe are constricted adjacent the lower end of the pipe, and an aperture is provided in the radial pipe above the constriction and adjacent thereto.

4. In combination, a fluid removal system for a rotary horizontal drum with a hollow trunnion; a hollow drum having its axis horizontal, horizontal trunnion means supporting said drum and having central axial bore means leading into the interior of said drum, said system comprising a stationary horizontal pipe extending axially through the said bore means of the trunnion means, a stationary radial pipe connected to and supported by said horizontal pipe and extending radially inside said drum toward the inner surface of the drum, a stationary intake nozzle on the radially outer end of said radial pipe, said intake nozzle comprising a hollow box-like structure, having one Wall on the radially inner side of said box-like structure provided with an aperture into which the radial pipe extends and providing a passage for communication of the radial pipe with the interior of said nozzle, said passage having a constriction in the region where the nozzle is connected to the pipe, said box-like structure including side walls extending in a substantially radially outward direction from the periphery of said radially inner Wall, said structure having its radially outer side open and surrounded by the radially outer edges of said side walls, said radially outer edges of said side walls defining the outer border of the nozzle and terminating in a region which is close to but spaced slightly from and substantially parallel to the inner surface of the drum and adapted to remain in said region during rotation of UNITED STATES PATENTS 2,617,205 11/1952 Cram 34124 2,987,305 6/1961 Calhoun 263-3 2,993,282 7/1961 Daane 34125 3,009,261 11/1961 Hieronymus 34-125 FREDERICK L. MATTESON, JR., Primary Examiner.

NORMAN YUDKOFF, PERCY L. PATRICK, WIL- LIAM F. ODEA, Examiners.

J. P. ROBINSON, C. R. REMKE, Assistant Examiners. 

1. A CONDENSATE REMOVAL SYSTEM FOR A HORIZONTAL DRUM WITH A HOLLOW TRUNNION, SAID SYSTEM COMPRISING A HORIZONTAL PIPE COAXIAL WITH THE TRUNNION, A STATIONARY RADIAL PIPE SUPPORTED BY AND EXTENDING SUBSTANTIALLY AT RIGHT ANGLES FROM THE HORIZONTAL PIPE AND AN INTAKE NOZZLE ON THE LOWER END OF SAID RADIAL PIPE, SAID INTAKE NOZZLE COMPRISING A HOLLOW BOXLIKE STRUCTURE COMPLETELY CLOSED ON ALL SIDES BY VERTICAL WALLS AROUND ITS HORIZONTAL PERIPHERY BUT WITH AN OPEN BOTTOM AND WITH AN APERTURED TOP CONNECTED WITH THE RADIAL PIPE AND PROVIDING A PASSAGEWAY IN COMMUNICATION THEREWITH, THE ENTIRE LOWER EDGE OF THE NOZZLE LYING IN AN APPROXIMATELY HORIZONTAL PLANE CLOSE TO BUT SPACED SLIGHTLY ABOVE THE INNER SURFACE OF THE DRUM AND ADAPTED TO REMAIN IN SAID PLANE DURING THE ROTATION OF THE DRUM. 